The present invention relates generally to blow molding apparatus of the type having movable mold sections for forming compression molded areas in a molded article and, more particularly, to blow molding apparatus of this type adapted for molding annular compression rings in a molded article.
Blow molding of thermoplastic material is a common and well known technique for forming hollow plastic bodies basically by extruding and inflating a tubular plastic parison within a mold cavity defined between mating mold halves movable toward and away from one another in a direction radially with respect to the parison to open and close the mold cavity. It is further known to provide one of the mold halves with auxiliary mold sections which are movable with respect to one another to form a compression molded area in the parison, e.g., for forming a handle opening in the molded article. Representative examples of this type of blow molding apparatus are disclosed in U.S. Pat. Nos. 3,342,916; 3,424,829; 3,438,538; 3,585,681; and 3,792,143. Other blow molding apparatus are known wherein each mold half is provided with two or more mold sections arranged for movement in a direction axially with respect to the tubular parison following initial inflation thereof within the mold to produce annular compression rings about the exterior periphery of the molded article, for example, to facilitate lifting and handling thereof. U.S. Pat. No. 4,170,623, discloses a representative example of blow molding apparatus of this type.